因为你是在一个对象中捕获的，你可以简单地在对象的构造函数中Assert这个事实：

public USTelephoneNumber implement TelephoneNumber {
   public USTelephoneNumber(String number) {
    // here you can handle +1 formats
    // But of course Canada also uses +1, so +1 is just a sanity check
    // but you can also apply much more sophisticated logic (like length, or using external validation.
     if (!number.startsWith("+1")){
        throw new IllegalArgumentException(String.format("%s is not a US number", number));
     }
     
     if (!number.replaceAll("[ ]","").replaceAll("+1","").matches("[0-9]+")) {
        throw new IllegalArgumentException(String.format("%s is not all numbers",number));

   }
}
@Throws(IllegalArgumentException.class)
public testIsNotUsPhoneNumber() throws IllegalArgumentException {
    new USPhoneNumber("+48 158 610 715");
}

public testIsUsPhoneNumber() {
    new USPhoneNumber("+1 425 388 2588");
}